There is no doubt that people have moral intuitions, and research — serious research is in very early stages — reveals that they are quite uniform without experience in complex situations, and in many ways surprising.
There is little reason to doubt David Hume’s observation that they are grounded in our nature — as we would restate it, adding nothing much substantive, in our genetic endowment. We can learn little bits about these topics by the methods of science, but the issues of human life so vastly exceed the range of scientific understanding that we are almost always proceeding on the basis of moral intuition, which is subject to reflection, debate, sharpening, etc., but cannot be grounded… The same is true of the epistemological intuitions that guide scientific research, in fact. Why should we seek what by our cognitive standards are simple, elegant theories? In brief, we have to live our lives, without immobilizing ourselves by posing questions that are very remote from answers, or even coherent formulation. That’s not to say we shouldn’t think about them, but without being immobilized by them.
What I’ve called truisms I think are moral truisms: for example, that we should apply to ourselves the same standards we apply to others (in fact, more stringent ones). Suppose I run into someone who doesn’t agree: say, someone who thinks it’s outrageous for someone to cause severe harm to us, but just fine for us to cause far more severe harm to them? Then discussion is pretty much at an end. However, I think this situation is very rare. The usual situation is denial that we are causing severe harm to them; rather, we are doing our best to help them, but sometimes failing because of our naivete, innocence, tendency to sacrifice ourselves too much for others, etc. That’s the essence of what in honest days used to be called “propaganda,” and is now called “news,” or “information,” or “sober commentary by public intellectuals,” or “scholarship,” etc. I think that is overwhelmingly true. One rarely comes across someone who says “I’m a Nazi and proud of it.” But if so, that reveals that there is something of a common moral ground, and a basis for constructive interchange — which may, and sometimes does, sharpen moral intuitions as well. We all know that very well in fact. It’s not that long ago, after all, that it was considered not just tolerable but in fact deeply moral to have slaves, beat one’s wife if she is disobedient, lash children, torture a poor person who robbed a crumb of bread, etc.